The application of pipeline pigs to clean, survey, and inspect pipeline systems is widespread over a number of different industrial fields. In the food and pharmaceutical industry, pigs (also known as pipeline scraper or mole) are typically employed for pipeline cleaning, and are used as an aid or means to push or scrape out or transport remaining products or residue materials in a pipeline. This helps to significantly reduce the quantities of cleaning fluid required for purging and flushing remnants out of the pipeline system such as before a subsequent manufacturing step. In some cases, pigs may also be used to recover valuable product from the line. Aseptic processing is typically a standard requirement for food industry and especially the pharmaceutical industry, leading to the development of pigging systems in which the pig is usually not physically removed from the system for inspection or for cleaning of the pig.
A reliable method for the detection, monitoring of a pig and its status and/or positioning within a pipeline system is consequently an essential feature for implementing aseptic pigging systems, especially for those designed without any means for visible inspection.
To locate them, pipeline pigs known in the art are often devised with one or more permanent magnet components. Such pigs are detected when they trigger magnetic field sensors fitted along the pipeline. For example, U.S. Pat. No. 5,400,456 describes an embodiment of a pig/pipeline scraper as comprising a centrally located, cylindrical permanent magnet, and another embodiment in which there are a plurality of permanent magnets circumferentially spaced around the annular groove portions of the scraper. The magnetic field generated by these are used to excite a detector located in a pipeline wall which indicates the presence of the scraper. An example of a position detector and system for detecting magnet-fitted pigs moving in a pipeline is described in EP1950525B1.
Such magnetic field-based positioning and detecting systems are capable of providing information regarding the location of a pig at a fixed time point i.e. at the time of detection. No information, however, can be provided by these systems as to other important data about the pig such as the identity of the pig or status information such as the time of its first launch. Other methods for providing data with respect to the location and status of the pig have been described in the art. For instance, pipeline pigs with acoustic or electromagnetic field-based communication systems have been disclosed. These pigs are typically used for inspecting, isolating or cleaning large pipelines such as water, sewage or oil pipes and usually also comprise sensors for measuring physical properties of the pipe and pipe environment.
For example, WO 2010/120189 describes a high-friction pig, such as those constructed for sealing off and isolating a selected part of a subsea oil pipeline, with a transponder for tracking and real-time monitoring. The pig moves when there is sufficiently high differential pressure across the pig; it forms a seal when at rest in the pipeline based on friction between the pig material and pipeline wall. The system allows two-way electromagnetic communication between the transponder mounted on the pig and a transceiver outside the pipeline. Each transponder is given a unique identification number, which is communicated to the transceiver; enabling an operator using the transceiver to track the pig's travel through the pipeline, and e.g. to determine when the pig has reached a pre-determined location in the pipeline. Further, the transponder in such pigs is configured to receive data from pig-mounted sensor(s) which monitor and acquire data on physical properties of the pipeline such as pressure or temperature upstream and downstream of the pig e.g. to ensure that the pig is properly in place and properly sealing the pipeline.
DE 10 2005 059 023 discloses a pipeline pig provided with a signal receiver/transmitter device that is useful for transporting media, in particularly fluid media, within a pipeline. The signal receiver/transmitter device provides a means for identifying the pig; however, this function works only when the pig is used in a pipeline system incorporating at least one special pipeline section with a ‘window or port’ made of a material such as glass that is permeable or transparent to electromagnetic field signals (e.g. radio waves). In other words, identification of the pig is only possible when the pig passes by or stops at this particular pipeline section which has external to it an interrogation signal transmitter unit. Such a pipeline pig is therefore severely limited in that it may not be used in any pre-existing pipeline set-ups that do not have such windows, at least not without necessitating significant pipeline re-design and additional costs. In addition, information such as the position of the pig at any other locations within a pipeline cannot be readily determined.
Moreover, DE 10 2005 059 023 does not specifically disclose the use of such a pig for aseptic processing, nor whether such a pig incorporating a communications device may be able to withstand harsh processing or sterilization conditions, for example, its ability to withstand steam-autoclaving for extended periods of time.
A pipeline pig that is suitable for use in aseptic processing, and that incorporates at least one transponder or radio-transmitting/receiving device as a control means for the positioning of the pig within the pipeline has not yet been made commercially available. A sales brochure with limited technical information from the applicant of DE 10 2005 059 023 describes a pig for product recovery and separation incorporating permanent magnets that is further equipped with a read-only (RO) transponder. This pipeline pig however relies on the presence of the magnets for positioning. The transponder device is only for identification purposes; it is not disclosed how the read-only transponder may be used to provide ‘complete documentation’ as indicated in the brochure, such as to collect, transmit or retain data such as with respect to the location of the pig or the environment surrounding the pig. It is also not disclosed how the transponder may be incorporated so as to avoid the potentially disturbing influence of the magnets that are also present within the pig on the transponder.
WO 2005/100733 describes cementing plug (or pipeline pig) for oil pipelines with one or more radio frequency identification (RFID) tags (read-only or read-write) for identification purposes. The RFID-tags may be embedded in a recess of the plug and/or affixed exteriorly to the plug. In order to protect the RFID tag(s) from shocks (pressure, impacts, thermal)—as may be encountered in a wellbore or during drilling and which may lead to failure of the RFID tag(s)—the tags are held in place by and encased in a heat resistant glue or adhesive, e.g. epoxy material. In addition, they are covered with further heat and/or impact resistant materials which are either wrapped around the circumference of the plug's body (e.g. RYTON® wrap) or in the form of a cap ring (e.g. made of magnetic or nonmagnetic metals, plastic, composite, polytetrafluoroethylene, fiberglass, ceramic, and/or cermet.) corresponding to and closing off the recess. Alternatively, the RFID-tags may be encased in a ring of protective material whose shape and configuration corresponds to the shape of the recess.
Irrespective of how the RFID tag is affixed to the pig, though, the fixing would inevitably result in surface imperfections such as ridges or creases where the different materials of the pig and the heat-protective material meet. While this may not cause many concerns in oil pipelines, such surface imperfections are highly undesirable for aseptic work conditions; they are harder to clean and facilitate microbial growth. Same applies e.g. to the very common shape of the wipers of the cementing plugs in WO 2005/100733; rendering most oil pipeline pigs unsuitable for aseptic work conditions.
Unlike the signal receiver/transmitter device in DE 10 2005 059 023, RFID tags do not require a transparent or permeable window to allow the identification of the pig. However, food- or pharma pipeline pigs are far smaller than oil pipeline pigs such as those described in WO 2005/100733. In consequence, permanent magnets (as currently used for the positioning of the pig in food and pharmaceutical industry) would get far closer to an RFID-chip than it would be the case in large oil pipeline pigs and thus increasingly interfere with the RFID's function. Due to this problem, RFID tags commonly have been disregarded for food- or pharma pipeline pigs.
It is therefore the object of the current invention to provide a pipeline pig for cleaning a pipeline or for pipeline product recovery comprising at least one radiofrequency identity tag which overcomes at least one of the problems or limitations associated with prior art pigs, in particular a permanent magnet-free pipeline pig comprising at least one radiofrequency identity tag as a positioning and monitoring means for the pig within the pipeline and also as an identification and/or data-collecting means which may be subjected to sterilization conditions and other high temperature and high pressure processing conditions. Another object is to provide a method for identifying, monitoring and/or positioning of a pipeline pig used for aseptic processing. Other objects will become clear on the basis of the description and the claims.